1. Field of the Invention
The present invention relates to a semiconductor device, and in particular, to a semiconductor device having a super junction structure and a method for manufacturing the same.
2. Description of the Related Art
Semiconductor devices, such as high voltage elements, are typically divided into: vertical double-diffused metal-oxide-semiconductor field effect transistors (VDMOSFETs) and laterally diffused metal-oxide-semiconductor field effect transistors (LDMOSFETs). In order to increase the withstand voltage of the described high voltage elements, the doping concentration of the deep well region (or referred to as the drift region) is reduced, the depth of the drift region is increased, or the length of the isolation structure (or referred to as the field oxide layer) underlying the gate is increased.
FIG. 1 is a cross section of a conventional n-type LDMOSFET. The n-type LDMOSFET 10 comprises a p-type semiconductor substrate 100 and a p-type epitaxial layer 102 thereon. A gate structure 116 and a field oxide layer 114 are on the p-type epitaxial layer 102. Moreover, a p-type body region 106 and an n-type drift region 104 are respectively in the p-type epitaxial layer 102 on both sides of the gate structure 116, wherein the n-type drift region 104 further extends into the underlying p-type semiconductor substrate 100. A p-type contact region 108 and an adjacent n-type contact region 110 (or both referred to as a source region) are in the body region 106 and an n-type contact region 112 (or referred to as a drain region) is in the drift region 104. Moreover, a source electrode 117 is electrically connected to the p-type contact region 108 and the n-type contact region 110. A drain electrode 119 is electrically connected to the n-type contact region 112. A gate electrode 121 is electrically connected to the gate structure 116.
As mentioned above, in order to improve the withstand voltage of the transistor 10, the doping concentration of the drift region 104 has to be reduced and/or the length of the field oxide layer 114 underlying the gate structure 116 has to be increased. However, when the withstand voltage is increased by the described ways, the on-resistance (Ron) or the size of the transistor 10 is also increased.
Thus, there exists a need in the art for development of a semiconductor device, capable of increasing the withstand voltage while preventing the on-resistance from increasing.